Method of and means for reducing the effects of electrical disturbances



May l, 1934. 1,956,689

ucING THE EEEEcTs 0E ELEcTRIcAL DISTURBANCES D. G. MccAA METHOD oF ANDuEANs Fon RED Filed Aug. 6, 1929 3 Sheets-Sheet 2 EHSU um May lv, 1934.D Q MCCAA 1,956,689

METHOD OF AND MEANS FOR REDUCING THE EFFECTS OF ELECTRICAL DISTURBANGESFiled Aug. 6,1929 3 Sheets-Sheet 3 Patented May 1, 1934 UNITED STATESScarce com PATENT OFFICE METHOD OF AND MEANS FOR REDUCING THE EFFECTS OFELECTRICAL DISTURB- ANGES David G. McCaa, Lancaster, Pa.

Application August 6, 1929, Serial No. 383,932

24 Claims.

My invention relates to improvements in means for reducing and limitinginterfering pulsations in electric circuits through which electricalenergy is being transmitted in useful form; and especially to apparatusand methods adapted to diminish the influence of atmospheric or anyother electrical disturbances in signal receiving devices, originatingexternally of the device; and is a continuation in part of the inventiondisclosed in my co-pending application, Serial No. 320,849 led November21st, 1928, which, in turn, is a division of my application, Serial No.74,087, filed December 8th, 1925.

As is well known, when electrical disturbances. are in evidence duringradio reception, they take the form of audible noises which oftencompletely submerge all other reproduced sounds. The origin of suchdisturbances cannot be readily controlled, nor their arrival at theantenna prevented; hence the place where their effects may be decreasedis confined to the vicinity of the receiving set itself. To lessen oreliminate the oscillations by which such disturbances are producedrequires of course that such oscillations be, so far as possible,nullified; and one useful method of proceeding for this purpose is todecrease the amplitude of said oscillations, as compared with theamplitude of signal oscillations.

Itis therefore the object of this invention to provide a method and anapparatus so designed that the effects of electrical disturbances can becontrolled and greatly reduced, and in fact largely neutralized, withoutin any way affecting the quality of reception of the desired signals;thus eliminating interference and permitting the reception of thesignals with virtually as much Xstrength and clearness as when nodisturbances ,are present.

A further object of the invention is to provide a method and apparatusthat will enable the., 3" electrical disturbances to be divided intoequal' components and to be substantially reduced, and lso controlledthat the divided components op-` pose each other, and are thereby inlarge meas reduction of the disturbances is'being accom- 1:,plished.

S Another object of the invention is to provide a method and apparatusby which the effect of electrical disturbances may be reduced to a pointwhere it is no longer troublesome, and which can be operated inconnection with an ordinary radio receiving set; the apparatus in thisrespect the signals to pass freely while the substantiall-,`

(Cl. Z50-20) including appliances which can be disposed either betweenthe set and the antenna, or connected into the circuit of the setbetween the point where the antenna is connected and the soundreproducing device.

A still further object is to provide apparatus for thus reducing theinfluence of electrical disturbances that can be easily andinexpensively constructed, that is reliable in operation and that caneither be incorporated into a receiving set, or made up as an accessoryto be connected to a radio receiving set in such manner as to give thedesired results.

Other objects and advantages of the invention will appear from thefollowing description taken in connection with the drawings.

On the drawings, Fig. 1 is a view showing diagrammatically anarrangement of circuits with the necessary appliances therein forrealizing the objects of my invention;

Figs. 2 to '7, inclusive, are similar arrangements giving modifications;and

Fig. 2a is a graphic representation of the function of coils 12 and 15of Fig. 2.

Referring first to Fig. 1, I show a pair of primary coils 1 and 2 inseries, the terminals of these coils 3 being arranged one for theconnection with the antenna (not shown), and the other with the groundin the usual way, or both to any other source of signal waves. Bothcoils are adapted to transfer energy to a secondary 6. Adjacent to thecoil l is a secondary coil 4 and cooperating with the coil 2 is asecondary 5. Each of the secondaries 4 and 5 has its terminals connectedto the anodes of two thermionic two element vacuum tubes '7 and 8, 7 and8' respectively. The cathodes of each 'pair of tubes '7 and 8, and 7 and8 are in the form of the usual heated filaments, and are connectedtogether and arranged to be supplied with current from common sources 9and 9' respectively. The current of each source 9 and 9 can becontrolled by a suitable rheostat connected with each of the g cathodes.At l0 is a uni-directional current source, the positive terminal ofwhich is joined o the cathodes of tubes 7 and 8 for the coil 4,

2and the negative terminal of which is connected to the anodes or platesvia the mid-point of the secondary 4. This secondary is thus in effectdivided into two coils, the upper of which is operatively associatedwith the adjacent tube 7 and the lower with the adjacent tube 8. Thecircuit of the secondary 5 includes similar tubes 7' and this source isreversed with respect to the source 10 and has its negative terminalconnected to the laments of the adjacent tubes 7 and 8' and its positiveterminal connected through the midpoint of the secondary 5 to the anodesor plates.

Obviously, a single uni-directional current source could be used inplace of sources 10 and 10 or sources 9 and 9. The positive and negativeterminals of sources 10 and 10' may be connected to combine them as acommon source. Likewise, the positive and negative terminals of sources9 and 9 may be connected to combine them as a single source. However, itis important to note that only one of these two connections may be made,since if both were made in the same system, a short circuit would beplaced across source 10 or source 10. Since a showing of the sources asindicated might be confusing, they have been shown as independentsources, but the above-mentioned modification is an obvious one.

The coils 1 and 2 are arranged in` opposition; that is they are so woundor poled that the passage of current through them causes the magneticflux of one coil to oppose that of the other. Further the voltage of thesource 10 is selected so as to be substantially equal to the peakvoltage of the oscillations carrying the signals.

Suppose, for example, signal oscillations are coming in and pass throughboth coils 1 and 2. As these coils are in opposition, they have nodirect effect upon the secondary 6; and as the voltage of theoscillations is no greater than that of the source 10, the anodes or theplates of tubes 7 and 8 connected with the coil 4, which are at anegative potential because they are connected with negative terminal ofthe source 10, remain negative. Hence there is no ow of space currentbetween the anodes and the cathodes of the tubes 7 and 8 of the coil 4;and the circuit of the coil 4 remains inoperative. On the other hand,the anodes of the tubes 'l' and 8 connected to the coil 5 are alwayspositive because they are connected to the positive terminal of thesource 10'. Hence signal oscillations passing through the coil 2 inducecorresponding oscillations in the coil 5. When the upper end of the coil5 is positive, the oscillations pass through the tube 7'; while thelower end of coil 5, which is connected to the anode of the tube 8', isat the same time negative, no oscillations pass through the tube 8.Similarly, when the lower end of the coil 5 becomes positive, the upperend becomes negative and oscillations pass through the tube 8' but nonethrough the tube 7. The tubes 7' and 8 thus act as resistors to bothhalves of the incoming signal wave and the magnetic flux from the coil 2is disturbed and intercepted by the two circuits of the coil 5,unbalancing the system and enabling the primary 1 to generate asubstantially unopposed voltage in the secondary 6. Hence signals aretransmitted to the circuits connected to the coil 6.

The upper coil 4 with its halves connected to valves 7 and 8, having anegative potential higher than the peak signal potential on the anodesdue to connection with the negative: terminal of the source 10, permitsno signal current to iow into the tubes 'l and 8 at this time.

If now atmospheric or other electrical disturbances of high amplitudeoccur and ow into the coils 1 and 2 with the signal oscillations, thevoltage induced in the coil 4 will be much higher than that of thesource 10. In this case, the tubes 7 and 8 connected to the coil 4 willpass current through their plate circuits and so will the tubes 7 and 8connected to the lower coil 5. As soon as current flows in the circuitsof the secondary 4, the flux generated by the coil 1 is intercepted anddisturbed by the two halves of the secondary 4. Similarly, thedisturbing oscillations and the signal oscillations passing through thecoil 2 inductively influence the coil 5 and current will now in thecircuits of this coil as before alternately through the tubes 7 and 8therein. The current in the circuits of the coil 4, however, will beproportional to the disturbing oscillations only; while the current inthe circuit of coil 5 will be proportional to both the disturbing andthe signal oscillations and will be larger to that extent. The ux of thecoil 2 will thus be largely intercepted by the secondary 5, while themagnetic flux of the coil 1 is intercepted only to the extent that isproduced by the disturbing oscillations in coil 4, and since the primarycoils 1 and 2 are arranged in opposition, the effect of the disturbingoscillations will be substantially nullified and only the signaloscillations will be transmitted by the secondary 6 to the receivingset.

Obviously, by choosing proper values of the biasing batteries l0 and10', the fluxes of the coils 1 and 2 can be disturbed to substantiallythe same extent for all high amplitudes. Therefore, whenever disturbingoscillations only are present, equal and opposite reduced voltages aregenerated thereby in the secondary 6, giving substantially no output inthe circuit of this secondary. When disturbing and signal oscillationscome in together, the disturbing oscillations are in effect arrested, orsubstantially reduced by the coils 4 and 5 and only the signals canpass; and when signal oscillations come in by themselves, they aretransmitted because of the unbalanced effect of the coil 1 on the coil6; the coil 2 being rendered inoperative. There may be a small componentof disturbing oscillations present in each of the prmary coils 1 and 2due to incomplete interception of their fluxes by secondaries 4 and 5respectively, but the components are equal and opposite, because of theopposed relation of coils l and 2, and are therefore balanced out andhave substantially no effect on the secondary 6.

Figure 2 shows a modified arrangement for producing the same effect, andparticularly adapted to be used in audio frequency circuits. The primarycoils 1 and 2 are associated with the secondary coils 4', 5 and 6 as inFigure 1 with the coil 6 leading to the set. In the circuit of secondary5 is a variable resistance 18, and choke coil C, designed to choke outoscillations of signal frequency. Associated with the secondary 4 aretwo closed iron cores 11 and 14 on which are wound two coils 13 and 16which are in series with a direct current source 17 and an adjustableresistance r. The function of the coils 13 and 16 is to saturate thecores 11 and 14 by means of the direct current source 1'7 and in serieswith them is another choke C. The saturation point may be adjusted bymeans of the resistance r. On the opposite legs of the cores are woundtwo coils 12 and 15 which are in parallel with each other and with thesecondary 4. 'Ihese coils 12 and 15 together with their cores 11 and 14respectively, function to produce an eiect similar to that produced bythe valves 7 and 8 in Figure 1.

The saturation point of the cores is set at such a predetermined valuethat the impedance of the coils 12 and 15 and consequently coil 4' willbe sufficiently high to prevent signal current from owing in the coil 4until the voltage across 4 is of such high value as to decrease theimpedance of' the coils 12 and 15, i. e., when signal voltages traversethe Winding 1, there will be no effect on the coils 12 and 15 becausethe voltages are of insufficient value to affect the impedances of thecoils 12 and 15, but as soon as disturbing voltages, which are generallysurges of high amplitude, traverse the winding 1, they inducecorrespondingly high voltages across the coil 4 thereby materiallydecreasing the impedance of coils 12 and 15 and permitting considerablecurrent to flow in the circuit of 4.

This function may be more clearly understood when explained by means ofthe graphical illustration shown in Fig. 2a. Curve a is thecurrent-impedance characterictic or saturation curve of the coil 12. Itmay be noted that the impedance remains constant until the saturatingcurrent 112 reaches the point i where it begins to take a sudden dropand continues to decrease with an increase of current. It is thissaturation point i that is made use of in the device of the invention.The direct current from the source 17 is set at such a value as c wherea substantial increase in current beyond that point will decrease theimpedance of the coil 12. Now if signal currents, which are small asindicated by d in Fig. 2a, traverse the winding 12, they will have verylittle or substantially no effect on the impedance of the coil asindicated by the curve in the region of the point i on the curve a. Onthe other hand when disturbing currents traverse the winding 12 asindicated by e in the figure they reduce the impedance considerably asindicated by the point g, and consequently the impedance of the circuit4 is reduced and considerable current will flow thereby disturbing theflux of coil 1 and elfectually absorbing substantially all of thevoltages or surges from coil 1 while permitting the signal voltages toremain in the circuit of coill.

It will be noted from Fig. 2a however that the coil 12 takes care ofonly one-half of each cycle, that is the portion to the right of thepoint 1I in decreasing the impedance of the coil. Therefore the coil 15is provided in parallel with coil 12 and arranged in such a way as totake care of the opposite half of the cycle, i. e., when the top of coil12 is positive the top of coil 15 will be negative and in this way bothhalves of the alternating current wave in coil 4 are taken care of. Thecurve b in the Fig. 2a is the curve of coil 15.

The operation of the coils 12 and 15 together with primaries 1 and 2 andsecondaries 4', 5' and 6 is as follows:-The coils 1 and 2 are wound orpoled so that the magnetic flux produced in them is equal and oppositeand when signal oscillations alone come in at the terminals 3, the coils1 and 2 being balanced produce no effect in the secondary 6. Coil 5'being closed through the resistance 18, the signal oscillations create amagnetic flux in primary 2 which is largely intercepted or absorbed bythe coil 5 thereby unbalancing the system and the same oscillations incoil 1 induce a current in the coil 6 permitting the signal to go to thereceiving apparatus. At this time, the circuit of coil 4 issubstantially open circuited because the signal voltages are notsufcient to increase the saturation of the cores 11 and 14.

When disturbing oscillations or undesired electrical surges arrivetogether with the signal oscillations, the amplitude is of course muchgreater and considerable current flows in the circuit of coil 5disturbing and intercepting the magnetic ux of coil 2 as before, so thatit has only a slight effect on coil 6; this slight effect being balancedout by the equal and opposite effect in coil 1. Now coil 4 also drawscurrent because of the effect of the disturbing voltages on thesaturated cores 11 and 14 through coils 12 and 15 but only to the extentthat the current induced by the disturbing oscillations is substantiallyabsorbed or intercepted from the coil 1 and the signal oscillations arepermitted to remain which are in turn induced by the primary l intosecondary 6 and are transmitted to the receiving apparatus.

It is readily seen that the function of coils 4 and 5 of Fig. 2 is thesame as in Fig. 1, that is, coil 5 absorbs substantially the total fluxproduced by both disturbing and signal oscillations in coil 2 while coil4 absorbs from coil 1 substantially only that portion of the flux whichis produced by the distributing oscillations. The system is therebyunbalanced and primary 1 induces the signal current into secondary 6which transmits it to the receiving device. The purpose of choke C incircuit 5 is to cause the phase angles of the two circuits 5 and 4 to besubstantially equal when disturbing oscillations flow in circuits 4 and5.

In the modification shown in Fig. 3, the coils 1 and 2 are in the samerelation as before, and the coil 5' has its terminals connected to thecoil 19. Between coil l and one terminal 3 is a transformer having aprimary coil 20 and a secondary coil 21. Another transformer isconnected with its primary 25 in series with the secondary 21. Thistransformer is used solely for producing proper phase relation betweenthe voltages across the coil 19 and coil 4 and is not in inductiverelation with either coils 20 and 21 or 1 and 4. One terminal of thesecondary 26 is connected to the grid of an amplier vacuum tube 22, andthe other is joined to the filament of this tube. The anode of the tube22 is connected to the positive terminal of the battery 24 and a primarycoil 23, also joined to the filament of the tube 22; and this coil 23 isin inductive relation with a secondary coil 19 in the circuit of thesecondary 4.

With this arrangement, disturbances and signals together are absorbed bythe action of the lower secondary coil 5', and disturbances only by theupper coil 4'. The method of keeping the upper secondary 4' to allintents and purposes open, so far as signal in primary 1 is concerned,is to subject it to the influence of an equal and opposite potentialwhich must not exceed the peak potential of the signal. When signaloscillations arrive, the primary coil 2 causes current to flow in thecoil 5 and its flux is intercepted so that it substantially does not actupon the secondary 6. The signal oscillations also act through theprimary 20 and so influence the amplifier tube 22 that the plate currentthereof varies between maximum and Zero. Hence in the coil 19 there isgenerated a voltage that is equal and opposite to the voltage producedin the secondary 4 by the coil 1, as indicated by signs and arrows. Thecoil 4' thus remains practically open and the flux of the coil 1 linkswith the coil 6 to transmit the signal to the receiving apparatus.

When signal and disturbing oscillations arrive together, the circuit ofthe lower coil 5' becomes active as before and intercepts almost all theflux from the coil 2. At the same time, the primary 20 transfers thecombined oscillations which are of much higher amplitude through circuit2l, 25 to the-coil 26; but in the circuit of this coil 26,

litem the oscillations now cannot be amplied because the vacuum tube 22becomes saturated or goes to zero before each oscillation or surgereaches its maximum Value. The transfer of energy from coil 23 to thecoil 19' is therefore proportional only to the signal strength, andreduces the voltage in the coil 4' accordingly. Therefore, the effectivevoltage of the coil 4' will be in proportion to the intensity of thedisturbing oscillations only, and the flux of the primary 1 will not bewholly intercepted by the coil 4'. The portion of the magnetic flux ofthe coil 1 due to signal oscillations can inductively affect the coil 6and the signal will be passed through again with the disturbancessubstantially reduced.

Another form of this modication may be made using two tubes A and B inparallel relation, as shown in Fig. 3a with the grid of one tube biasedpositively and the grid of the other tube biased negatively, in place ofthe single tube 22 shown in Fig. 3. This arrangement overcomes thedifficulty which might arise from the variation of the saturation pointof vacuum tubes now in commercial use and which might not be taken careof in the circuit of Fig. 3. In Fig. 3a, the positively biased tube Apasses both the disturbing oscillations and the signal oscillationswhile the negatively biased tube 3 passes only the disturbingoscillations because the value of the biasing voltages is equal to orgreater than the peak signal voltage. Consequently, when the positivepeak of the signal voltage acts on tube A plate current flows but whenthe negative peak of the signal acts on tube A the plate current fallsto zero. The negatively biased tube B, however, remains inactive to bothpeaks of signal voltage. When the positive peak of the disturbingvoltage acts on the tube A, plate current will flow as in the first casebut when the negative peak acts on tube A, the plate current falls tozero and beyond. When the positive peak of the disturbing voltage actson tube B, plate current will also flow but will oppose the platecurrent of tube A in coil 23 so that there is no output due todisturbing voltages and only the plate current of tube A due to signalvoltages will be translated from coil 23 to coil 19'. This may be moreeasily understood from the following table, in which it is apparent thatsignal is transferred without opposition, and disturbances generatesubstantially equal currents in both tubes.

In Fig. 4, the circuits comprise primaries 1 and 2 wound so that theirmagnetic fluxes are in opposition and connected to terminals 3 asbefore, with the secondaries 4' and 5', associated with coils l and 2,respectively, and the secondary 6 between the primaries 1 and 2 andassociated with both. The lower secondary 5 has the coil 19 in itscircuit and the upper secondary 4' has the coil 19'. At 43 is a localsource of alternating current connected in circuit with two coils 44 and44' which are in inductive relation to the coils 19 and 19',respectively. This source 43 generates a synchronous alternatingcurrent, being a current of the same frequency and substantially thesame amplitude as the signal current to hold the secondaries 4' and 5open. The

coil 19 is adjacent coil 44 and the direction of the current from thesource 43 is such that the signal voltage across the upper secondary 4is opposed in amplitude and phase by the voltage induced in coil 19'from the source 43 while the signal voltage across the lower secondary5' is in phase with the voltage induced in coil 19 from source 43, asthe arrows and signs indicate. For signals alone the circuit of thelower coil 5 only will be energized to intercept the ux of primary 2, sothat the coil 6 is affected by the magnetic flux of the coil 1,substantially no current flowing in the coil 4', because the signalcurrent is opposed by the current from source 43. When signals anddisturbances come in together, the same result occurs with regard to thecoil 5', but the oscillations of larger amplitude will now take effectin the coil 4 to overcome the voltage due to the local source 43. Thecurrent in the coil 4 will again not be as great as current in the coil5', leaving the primary l unbalanced to an extent proportional to theamplitude of the signal oscillations to take effect on the coil 6 and totransmit the signals. The arrangement of Fig. 4 does not transfer localoscillations into the circuit of terminals 3-3 because coils 19 and 19are arranged in opposed relation with respect to the input. If desirablea non-synchronous frequency may be used, in which case coils 4 and 5'alternatively function to absorb the opposing signal flux.

In Fig. 5, coils 1 and 2 are in opposition as before and are connectedto the antenna 25 and to the ground, with an adjustable condenser 26 inthe antenna circuit. The coil 6 in the same position as before isbridged by an adjustable condenser 42. The secondary 5' cooperating withthe primary 2 is in circuit with an adjustable resistance 18. The coil 1cooperates with a secondary in two sections, consisting of coils 27 and28. These coils are connected through coil 29 in series; and themid-point of the coil 29 is united by the connector 32 with theconnection joining the two cathodes of a pair of three-element vacuumtubes 31, 31. The other terminals of the coils 27 and 28 are connectedwith the anodes of the tubes 31 and the cathodes are supplied withcurrent from source 9. A coil 33 is in inductive relation to coil 29 andthe opposite terminals of this coil 33 are joined to the grid and lamentof another three-element amplifying vacuum tube 35. The grids of thetubes 31 are joined to the opposite ends of the two coils 38 and 39, inseries; making a single coil in inductive relation to coil 37 which isin circuit with the uni-directional source 36 across the anode andfilament of the amplier tube 35. A direct current source 10 united tothe common terminal of the coils 38 and 39, and to the cathodes of tubes31 biases negatively the grids of tubes 31.

In this arrangement, the primary input and the secondary output circuitsare tuned. A Voltage will be generated across the windings 27 and 28 byboth the disturbing oscillations but the signal voltages will not causecurrent to ow in the anode circuits of tubes 31 because they are notenough to overcome the negative bias on the grids produced by source 10.The disturbing voltages being of much greater amplitude oppose theeffective negative bias on the plates and cause a current to flow in theanode circuits of the tubes 31. This anode current flowing through coil29 induces a voltage across coil 33 which acts on the amplifier tube 35.Here the voltage is amplified and transferred by the windings 37, 38 and39 to the grid-filament circuits of the two Valves 31, 31. The amplifiedvoltage may be higher than the voltage of source 10 and consequently mayovercome the grid biasing potential and a substantially increasedcurrent iiows in the anode circuits of tubes 31 thereby enhancing theaction of coils 27 and 28 in substantially the flux from primary coil 1produced by the disturbing oscillations.

The purpose of this circuit is to cause the valves 31 to operate withincreased effect by reason of lower impedance as compared to the valvesin Fig. 1 which are not connected to an amplier. When this system isconsidered as a trigger-actuated system the effect becomes moreapparent. Detuning also takes place in the primary and secondary tunedcircuits.

Hence when signals come in, the lower secondary 5 as before prevents thecoil 2 from energizing coil 6; unbalancing the system and allowing coil1 to transmit the signals through its inductive effect on coil 6.Inasmuch as the grids of the tubes 31 are biased, the signal voltagewill be insuicient to cause a flow of current in the Valves 31 and thesecondary circuit of the coils 28 and 29 remains open.

When signals and disturbances come in together, current corresponding toboth flows in the coil 5', drawing substantially all the magnetic iiuxof the coil 2 away from the coil 6; but in the secondary circuit of theprimary 1, a somewhat smaller current will flow in the circuit of coils27 and 28 and between the plates and filaments of tubes 31, due to thebiasing effect of battery 10, and the current thereby induced in thewinding 33 is amplied by the tube 35 as above set forth. The currentacts through the transformer coils 37, 38 and 39 and so affects thegrids of the valves 31 that current through the plate circuits of ythevalves 31 is increased. This current enables coils 27 and 28 tointercept the major part of the flux of the primary 1, due to disturbingsurges, and the coil 1 thus aifects coil 6 only enough to induceoscillations therein corresponding to the strength of the signals.'I'hus the effect of electrical disturbances or undesired oscillationsof high amplitude is reduced to a minimum. Fig. 6 again corresponds toFig. 1, except that no secondaries are used and crystals or heater tubesor other asymmetric conductors are substituted for the tubes shown at 7and 8 in Fig. l. The coils l and 2 are wound in opposition upon theopposite ends of an iron core 45 which may have a central leg 46. Thisiron core is used to make the system more effective at audiofrequencies. Cooperating with the coil 1 is a coil 47 and cooperatingwith coil 2 is a coil 48, these two coils 47 and 48 are connected inseries and lead to the receiving set. Across primary coil 1 areconnected two pairs of crystals or other asymmetric conductors 50a witha D. C. source 51 in such a manner that one pair of crystals will permitone half of an alternating current to pass through while the other willpermit the other half to go through as in a full wave rectiiier. Thevoltage of source 51 is set at a value equal to or greater than the peakvoltage of the signals so that no signal oscillations can traverse thevalve circuit 50. In parallel with primary 2 is an adjustable resistor49.

The coils 1 and 2 would generate equal and opposite voltages insecondary lcoils 47 and 48 if it were not-for the presence of theresistance 49 and the valve circuit 50 containing crystals However whendisturbing oscillations arrive at terminals 3 together with signaloscillations the resistor circuit 49 absorbs both while the valvecircuit absorbs only to the extent to which disturbing oscillations arepresent, the desired oscillations thereby generating the signal voltagesin secondary 47 which are transmitted to the receiving circuit.

Fig. 6a shows a modification of a Valve circuit which can be used inplace of the valve circuit 50 in Fig. 6 or in place of tubes 7 and 8 inFigs. 1 and 7. Two tubes 50h are substituted for the crystals 50a inFig. 6 and are reversely arranged, the anode of vone and the cathode ofthe other are bridged by a direct current source 51 and the resistance Rin parallel with the source while the opposite electrodes are directlyconnected.

In Fig. 7, the antenna 25 is connected through an adjustable condenser26 and two sets of coils 1, 52 and 2, 53 in parallel to ground. Thecoils 1 and 2 are arranged in opposed relation to each other as inFig. 1. The coil 52 at the left is inductively related to a secondarymade up of two windings 54 and 55 in series. These windings areconnected to. the anodes of two two-electrode thermionic vacuum tubes 7and 8, and their common terminal is connected to the filaments of thesetubes through'a source 10 with an adjustable voltage divider acrossitsterminals, the arrangement being similar to that shown in Fig. 1 forcoil 4. At the right, the coil 53 is ininductive relation with secondary5', which is shunted by a variable resistance 18. In inductive relationwith the primary coils 1 and 2 is the output coil 6 which Vis shunted bythe Variable condenser 42. The terminals of the coil 6 and condenser 42are connected to the grid and iilament of a detector tube 35. In circuitwith the grid are the usual leak resistance 57, and grid condenser 58;and the plate of tube 35' is connected through a unidirectional sourceof voltage 59 and telephones or loud speaker 60 to the filament of thetube. In the circuit leading to the grid is a primary 19 which has asecondary 44 supplied with alternating current from the local source 43controlled by a switch 56, if it be desired to use heterodyne reception.

In this circuit when signal oscillations alone'arrive at the antennathey are divided so that a portion goes through coils 1 and 52 to groundwhile another portion goes through coils 2 and 53 to ground. The coil 53being in inductive relation with the load circuit 518 is effectivelyshort circuited and its impedance decreased so that considerablymorecurrent flows through coil 2 than coil 1 because the impedanceof coil 52remains unchanged since the plate circuits of tubes 7 and 8 areeifectively open circuited to signal oscillations by the biasing'source10. In this way coil 2 has a greater inducing effect than coil 1 onoutput coil 6 and signals are translated into the output circuit.

When disturbing oscillations arrive alone the impedance of coils 52 and53 is decreased equally because the tubes 7 and 8 draw current as wellas the circuit 5'-18 and therefore equal currents flow in coils 1 and 2;but the coils are in opposition and the fluxes balance each other out sothat no disturbances are transferred to output coil 6.

When disturbing oscillations arrive together with signal oscillationscoil 53 draws more current than coil 52 because the impedance of coil 53is decreased more than that of coil 52 to the extent that circuit 5'-18is affected by the disturbing oscillations as well as signaloscillations while tubes 7 and 8 are affected only in proportion todisturbing oscillations. Therefore the coil 2 carries more current thancoil 1, the difference being the amount of signal current. Thedisturbing components in coils 1 and 2 are equal and opposite andbalance out while coil 2 translates the signal component to coil 6.

The disturbing oscillations take the frequency to which the circuit istuned by shock excitation while the signal oscillations retain theirnormal frequency and are slightly attenuated by the detuned circuit.Consequently the primary and secondary circuits are detuned from eachother when disturbing oscillations are present and therefore only a lowtransfer of energy takes place.

All of the modifications described are adapted to be used reversely,that is, the output may be used as the input and vice versa, and thecrcuits will function equally well. The device may be placed in circuitanywhere between the antenna and the reproducer.

Although for purposes of illustration, description and explanation, Ihave shown the coils l and 2 as the input and the coil 6 as the outputthey may be interchanged and I desire to be limited only by the scope ofthe appended claims.

I claim:

1. The method of reducing the effects of electrical disturbances onsignal oscillations which comprises dividing said disturbances intocomponents, substantially reducing said components and causing saidcomponents to oppose each other so that their effects on the signaloscillations are substantially eliminated.

2. The method of reducing the effects of electrical disturbances onsignal oscillations which comprises dividing said disturbances intocomponents without frequency discrimination, substantially reducing saidcomponents and causing said components to oppose each other so thattheir effects on the signal oscillations are substantially eliminated.

3. The method of reducing the effects of electrical disturbances onsignal oscillations which comprises separating the disturbances from thesignal oscillations in accordance with their amplitudes, dividing saiddisturbances into components, intercepting the major portion of saidcomponents and causing the remaining reduced components to oppose eachother so that their effects on the signal oscillations are substantiallyeliminated.

4. The method of reducing the intensity of electrical disturbances inradio reception which consists of producing magnetic fluxes in two coilswhich oppose in their eects on a third coil, reducing the value of fluxfrom one coil when the amplitude of the current therein is low, andreducing the Value of flux from the other coil when the amplitude of thecurrent therein is high.

5. The method of reducing the intensity of electrical disturbances inradio reception which consists in operating a pair of coils so that themagnetic flux of one coil opposes that of the other, intercepting theflux of one coil when the amplitude of the current therein is low, andintercepting the flux of the other coil only when the amplitude ofcurrent therein is high.

6. The method of reducing the effects of undesired oscillations ondesired oscillations which consists in producing a magnetic flux in apair of coils having a common flux path by passing both the undesiredand the desired oscillations through said coils and dissipating the fluxof both of said coils to such an extent as to prevent the undesiredoscillations from being translated into an output circuit while thedesired oscillations are translated to said output circuit unopposed.

7. The method of reducing the effects of undesired oscillations ondesired oscillations which consists in operating a pair of coils so thatthe magnetic flux produced by both of said oscillations in each of saidcoils is equal and opposite and intercepting the major portion of themagnetic flux of one of said coils while intercepting only that portionof the magnetic flux which is produced by the undesired oscillations inthe other of said coils and utilizing the remaining flux in said lastmentioned coil to transfer a desired current into a secondary circuit.

8. The method of separating desired oscillations from undesiredoscillations which comprises operating a pair of coils having a commonflux path in opposed relation to each other so that only one of saidcoils transfers said desired oscillations into an output circuit whilethe other of said coils transfers the undesired oscillations into acircuit in which they are dissipated.

9. The method of separating desired oscillations from undesiredoscillations which comprises operating a pair of coils in opposedrelation to each other so that the undesired oscillations are dissipatedfrom one of said coils and both the desired and undesired oscillationsare dissipated from the other of said coils and translating the desiredoscillations from the rst mentioned coil into an output circuit andutilizing said desired oscillations to operate a receiving device.

10. A device for separating desired oscillations from undesiredoscillations comprising a plurality of coils substantially equallysupplied with signal energy and in opposed relation, said coils having acommon flux path, an output circuit,

and means for controlling said coils so that only one of them translatesthe desired oscillations into said output circuit.

11. A device for separating desired oscillations from undesiredoscillations comprising a plural- 1 ity of primary coils in seriesopposed relation, a plurality of secondary coils in inductive relationwith said primary coils, one of said secondary coils being in the outputcircuit of said device,

means associated with another of said secondary 135 coils for rejectingthe desired oscillations from'ir said last mentioned secondary andcausing themg' to be translated into said output circuit, andi; meansassociated with still another of said secondary coils for interceptingthe undesired oscil-l1 G ondary coil in inductive relation with anotherof said primary coils, means associated with said additional secondarycoil for intercepting both the desired and undesired oscillations, and athird secondary coil in inductive relation with at least one of saidprimary coils for translating said ejected desired oscillations to areceiving circuit. 13. Apparatus for separating desired oscilla- '2tions from undesired oscillations comprising a \.f pair of coilsconnected in series and Wound so that the magnetic fluxes of said coilsare equal and opposite, a coil inductively related to said coils and asecondary circuit associated with each of said first mentioned coils andcontaining devices for causing the magnetic fluxes of said coils to bedissipated so as to suppress the undesired oscillations and allow onlythe desired oscillations to be translated into an output circuit.

14. Apparatus for reducing the eiects of electrical disturbances onsignal currents comprising a pair of primary coils connected in seriesand Wound so that the magnetic fluxes of said coils are equal andopposite, a secondary output coil in inductive relation with saidprimary coils, a secondary circuit in inductive relation with each ofsaid primary coils, one of said secondary circuits containing devicesfor causing the magnetic flux produced by the desired oscillations inone of said primary coils to induce a current in said output coil, andthe other of said secondary circuits containing devices for causing theflux produced by both the desired oscillations and the undesiredoscillations in the other of said primary coils to have substantially noeffect on said output coil.

15. Apparatus of the kind described comp-rising a pair of primary coilsin series opposed relation, a secondary output coil in inductiverelation With said primary coils, a secondary circuit in inductiverelation with each primary coil, a thermionic vacuum tube and a sourceof uni-directional current in each of said secondary circuits, thesource in one of said secondary circuits having its positive terminalconnected to the anode of its associated tube and the source in theother of said secondary circuits having its negative terminal connectedto the anode of its associated tube, another terminal of each secondarycircuit being connected to the cathode of its associated tube.

16. In combination with a pair of primary coils connected in seriesopposed relation, a secondary output coil in inductive relation withsaid primary coils, a pair of additional secondary coils in inductiverelation one with each of said primary coils, a pair of thermionicvacuum tubes having their plates connected to the terminals of one ofsaid secondary coils with a potential negative With respect to thecathodes applied to said plates through the mid-point of said secondarycoil, and a second pair of thermionic vacuum tubes having their platesconnected to the terminals of the other secondary coil with a potentialpositive with respect to the cathodes applied to said plates through themid-point of said other secondary coil.

17. In combination With a pair of primary input coils substantiallyequally supplied with signal energy and in series opposed relation, anoutput secondary coil in inductive relation with said primary coils, apair of auxiliary secondary coils in inductive relation with saidprimary coils, and means energized from the circuit of said primarycoils for producing a voltage opposing the voltage of one of saidauxiliary secondary coils.

18. In combination with a primary input coil, a pair of secondary outputcoils in series opposed relation and in inductive relation with saidprimary coil, a pair of auxiliary primary coils in inductive relationwith said secondary coils, and means energized from the circuit of saidsecondary coils for producing a voltage opposing the voltage of one ofsaid auxiliary primary coils.

19. An apparatus of the kind described comprising a pair of primarycoils in series opposed relation, a secondary output coil, a secondarycircuit coupled to each primary coil, a local source of voltage, andmeans for enabling said source to oppose the voltage in one secondary icuit and assist the voltage in the other.

' 20. Apparatus of the kind described comprising a pair of primary coilsin opposed relation, a secondary output coil in inductive relation withsaid primary coils, a secondary circuit associated With each primarycoil, one of said secondary circuits being closed through an adjustableresistance, a pair of secondary coils in series With a third coil in theother secondary circuit, a pair of vacuum tubes, each having a grid,plate and i'ilament, the plates of said vacuum tubes being connected tosaid secondary coils and their filaments connected to the mid-point ofsaid third coil, an amplier tube having a grid, plate and lament, thegrid of said amplifier tube being inductively coupled to said third coiland the plate of said amplier tube being inductively coupled to thegrids of said rst mentioned vacuum tubes, and means for applying anegative bias to at least one of said grids.

21. Apparatus of the kind described comprising a pair of primary coilsconnected to each other, a common iron core on which said coils areWound, a pair of secondary coils in series, one associated With eachprimary coil, said secondary coils being connected in opposition, anadjustable resistance shunting one primary coil, and a circuit includingan asymmetric valve shunting the other. '190 22. A device for separatingdesired oscillations from undesired oscillations comprising a pair ofcoils in series opposed relation, a coil in inductive relation With saidcoils, and an electrical circuit which is effectively open circuited tothe desired oscillations and closed to the undesired oscillations ininductive relation to one of said rst mentioned coils.

23. A system for reducing the effects of electrical disturbances onsignal currents comprising 1Q() an input circuit and an output circuit,an auxiliary circuit inductively coupled to one of said circuits andcontaining means for keeping said auxiliary circuit effectively open tosignal currents and closed to the disturbing currents there- 13g bycausing said signal currents to be transferred ,f to said outputcircuit.

24. The method of operating upon a complex Wave of signal and staticoscillations to improve the signal-static ratio which comprises dividingthe complex wave into tWo opposing components, weakening one componentand transferring it to an output circuit, and weakening the othercomponent only for high amplitudes before transferring it to saidcircuit.

DAVID G. MCCAA.

